TLR9 and Spondyloenchondrodysplasia with immune dysregulation: Based on earlier work suggesting that intracellular OPN couples the TLR9/MyD88 signalling complex to IFNα expression in pDCs in mice (12), An et al. (13) suggested that the autoimmune features of SPENCD might relate to a failure of mutant TRAP to dephosphorylate OPN in pDCs in humans, leading to persistent TLR9 signalling.